[1] Peking Union Med Coll, Dept Epidemiol, Beijing 100730, Peoples R China
[2] Peking Union Med Coll, Sch Nursing, Beijing 100730, Peoples R China
[3] China Ctr Dis Control & Prevent, Div Policy & Informat, Natl Ctr AIDS & STD Control & Prevent, Beijing, Peoples R China
[4] Shijingshan Dist Ctr Dis Control & Prevent, Beijing, Peoples R China
[5] China Ctr Dis Control & Prevent, Div Hlth Educ & Behav Intervent, Natl Ctr AIDS STD Control & Prevent, Beijing, Peoples R China